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D L Wetzel

Publications and source records attributed to D L Wetzel.

16 recordsLinked to original sources
PubMed2003

Enhanced potential for metabolic studies using narrow-band sensitized FT-IR microspectroscopy.

The ability to detect and measure the relative concentration of deuterated substance found in tissue specimens is enhanced by adding a custom made-to-order 50 microm narrow MCT band that has an optimized response profile for the CD, ND and OH absorption bands. In the short range of interest it has a 2:1 signal advantage over the stock MCT detector and the steep cut off before the finger print region significantly diminishing the noise. The result is that levels of specific deuterated compounds experimentally administered to biological systems and dispersed by the host organism can be detected and measured The custom small target size narrow-band detector with increased signal and reduced noise enhances the potential for the use of FT-IR microspectoscopy as a novel way to study metabolism without the use of radioactive materials.

Chemistry Techniques, Analytical↗
PubMed2001

Single fiber analysis by internal reflection infrared microspectroscopy.

Attenuated total reflection (ATR) is a convenient mode for single fiber analysis by infrared microspectroscopy, particularly when transmission spectra are difficult to obtain or when surface preferenced sampling is desirable. Textile finishes such as spin finishes, anti-static finishes, and permanent press finishes are revealed by ATR techniques. Bicomponent fibers may be analyzed by a combination of ATR techniques, transmission techniques, and spectral subtraction.

Journal Article↗
PubMed2000

Chemical changes in the photoreceptor outer segments due to iron induced oxidative stress: analysis by Fourier transform infrared (FT-IR) microspectroscopy.

Oxidative stress is thought to be an important pathogenic mechanism in many diseases of the retina. The purpose of this study was to investigate the chemical changes that are present in the photoreceptor outer segments of the retina following exposure to oxidative stress. Fourier transform infrared (FT-IR) microspectroscopy enables the characterization and semi-quantitation of chemical functional groups in microscopic regions of tissue sections. This technique was used to evaluate the chemical changes in the outer segments following exposure to ferrous sulfate, which promotes oxidative tissue damage. A reduction of C=C-H and C=O functional groups was observed in the outer segments of iron-injected eyes compared to vehicle-injected eyes at 3 days following injection, which is prior to major histological changes that occur by 7 days. These functional groups are found in docosahexaenoic acid (DHA), which is present at a high concentration in the outer segments. DHA contains a series of six cis-conjugated double bonds, which are vulnerable to free radical attack, and the reduction of these unsaturation group absorptions suggests that DHA was degraded and/or removed from the outer segments. An unexpected finding was that several other chemical functional groups increased in concentration over time in the outer segments of vehicle-injected eyes compared to non-injected eyes. These increases generally did not include C=C-H or C=O, which suggests that either DHA was being degraded while other organic molecules were being concentrated, or that production of DHA failed to be upregulated in vehicle-injected eyes. In summary, there was a loss of both C=C-H and C=O functional group concentrations in the outer segments of iron-injected eyes, and there was an increased concentration of several other chemical functional groups following trauma induced by vehicle injection.

Animals↗
PubMed1999

Microchemical analysis of retina layers in pigmented and albino rats by Fourier transform infrared microspectroscopy.

Fourier transform infrared (FT-IR) microspectroscopy is a powerful technique that can be used to collect infrared spectra from microscopic regions of tissue sections. The infrared spectra are evaluated to chemically characterize the absorbing molecules. This technique can be applied to normal or diseased tissues. In the latter case, FT-IR microspectroscopy can reveal chemical changes that are associated with discrete regions of lesion sites, which can provide insights into the chemical mechanisms of disease processes. In the present study, FT-IR microspectroscopy was used to analyze sections of retina from normal (pigmented) and albino rats. The outer segments of retinas from pigmented animals were found to have unusually strong absorption values for C&z.dbnd6;C-H unsaturation and carbonyl functional groups. Docosahexaenoic acid (DHA), a major constituent of lipids in the outer segments, also had particularly high absorption values for these functional groups, which suggests that it is responsible for those enhanced absorption values. Absorbance values for the unsaturation and carbonyl functional groups were substantially reduced in the outer segments of retinas from albino animals. This finding, together with data from other studies on light-induced oxidative events in the retina, indicates a loss of DHA by a light-induced mechanism in albino animals. The outer nuclear layer had strong absorbance values for H-C-OH and P&z. dbnd6;O functional groups, which is likely due to the sugar phosphate backbone of DNA. The outer and inner plexiform layers were found to contain greater concentrations of CH(2) and C&z.dbnd6;O functional groups than the outer and inner nuclear layers, which is due to the high concentration of synaptic connections in the former layers. In summary, FT-IR microspectroscopy revealed a unique chemical profile in the outer segments compared to other retinal layers, and this profile was altered in albino animals.

Animals↗
PubMed1998

Chemical analysis of multiple sclerosis lesions by FT-IR microspectroscopy.

Fourier transform infrared microspectroscopy can be used to collect infrared spectra from microscopic regions of tissue sections. If spectra are collected along a grid pattern, then maps of chemical functional groups can be produced and correlated to tissue histopathology. In the present study, white matter from multiple sclerosis and control brains were examined. Mapping experiments were designed such that 17 spectra were collected at 200 microm intervals along a line that was partially or wholly within a multiple sclerosis lesion site or within a representative white matter region of control tissue. Data analysis was based on earlier in vitro studies which found that the carbonyl at 1740 cm(-1) increases when lipids become oxidized (Free Rad. Biol. Med. 16:591-601, 1994), and the amide I peak at approximately 1660 cm(-1) broadens when proteins become oxidized (FEBS Let. 362:165-170, 1995). The results indicated that the C=O to CH2 ratio (1740 cm(-1):1468 cm(-1)) was elevated at several collection points in lesion sites from multiple sclerosis brains compared to values from white matter of control brains. Inspection of the amide I peak at 1657 cm(-1) revealed that it was broadened towards 1652 cm(-1) in multiple sclerosis tissues but not control tissues. These results suggest that lipids and proteins could be oxidized at active multiple sclerosis lesion sites. The localization of these products to lesion sites supports a role for free radicals in the pathogenesis of multiple sclerosis.

Aged↗
PubMed1998

FT-IR microspectroscopic detection of metabolically deuterated compounds in the rat cerebellum: a novel approach for the study of brain metabolism.

Deuteration provides a novel means for studying metabolism in biological organisms and avoids the use of radioisotopes. Ingestion of D2O enriched drinking water causes deuterium to be metabolically incorporated into molecules within tissues. The incorporation of deuterium into various chemical functional groups then can be monitored via infrared spectroscopy. The excellent spatial resolution that can be achieved with Fourier transform infrared (FT-IR) microspectrometers allows collection of infrared spectra from select microscopic regions of tissue specimens. Thus, combining deuteration together with FT-IR microspectroscopy enables analysis of metabolic activities by probing subregions within the microscopic field. In the present study, adult rats were given drinking water containing 30% or 40% D2O for 5 1/2 weeks. Frozen sections were prepared from the cerebellum, and infrared spectra were collected from the molecular layer, granule cell layer and white matter with FT-IR microspectrometers, using both conventional and synchrotron sources. The CD:CH and ND,OD:NH,OH ratios were highest in the molecular layer and lowest in the white matter. The high ratios in the molecular layer are consistent with the active synthesis and recycling at synapses, which are abundant structures in this layer. The low levels in the white matter are consistent with radioactive measures that found slow turnovers of proteins and lipids in myelin, which is the main constituent of white matter. In addition to describing the metabolic incorporation of deuterium, a graphic description of the distribution of chemical functional groups in the various layers of the cerebellum is presented. In summary, this study demonstrates that FT-IR microspectroscopy in conjunction with administration of D2O in drinking water can be used to reveal relative metabolic activities in various layers of the cerebellum. We predict that metabolic activities in other tissues and tissues in different states, e.g., disease states, can be analyzed in a similar manner.

Animals↗
PubMed1998

Ultraspatially-resolved synchrotron infrared microspectroscopy of plant tissue in situ.

Routine use of 6 microm or 12 microm apertures with synchrotron microspectroscopy provide good spectra without excessive co-addition of scans. 100% mapping by stepping in pixel sized increments reveals chemical heterogeneity within cellular dimensions. The brightness of the synchrotron source and the absence of thermal noise compared to a conventional thermal (globar) source yields favorable signal-to-noise operation. The nondivergent characteristics of the source result in minimal loss of radiation at the aperture, hence, spatial resolution approaches the diffraction limit. Details of cellular dimensions are then localized within any maps produced and individual spectra obtained from adjacent pixels clearly shows the striking difference in chemistry even within a microscopic vicinity. In this report the mapping of plant tissue with the synchrotron is contrasted to previous lower spatial resolution mapping experiments done with the globar on similar materials using interpolation between separated sampling spots and larger apertures.

Absorption↗
PubMed1996

In situ characterization of beta-amyloid in Alzheimer's diseased tissue by synchrotron Fourier transform infrared microspectroscopy.

We report the first evidence of the structure of beta-amyloid protein as it exists in situ within a slice of human Alzheimer's diseased brain tissue. Using a Fourier transform infrared microspectroscopic technique, areas of interest can be selected for spectral measurements with regions of potential contamination masked. In so doing, it is possible to obtain infrared spectra only of beta-amyloid and not the surrounding grey matter within which it lies. However, to obtain spectra of high-quality signal-to-noise ratio using a conventional infrared source, we were limited to aperture sizes between 24 microns x 24 microns to 50 microns x 50 microns. Markedly improved high-quality spectra were acquired with infrared radiation provided by a synchrotron light source (National Synchrotron Light Source, Brookhaven National Laboratories), using aperture sizes as small as 12 microns x 12 microns. This allowed spectroscopic mapping of brain tissue regions containing amyloid. We observe that in situ protein of grey matter exist predominantly in an alpha-helical and/or unordered conformation, whereas within amyloid deposits a beta-sheet structure predominates. The hydrogen bonding strength of the beta-structure found in situ is different from that reported in the literature for isolated/chemically synthesized beta-amyloid peptides.

Alzheimer Disease↗
PubMed1994

Neuropathology of twitcher mice: examination by histochemistry, immunohistochemistry, lectin histochemistry and Fourier transform infrared microspectroscopy.

The twitcher mouse is an authentic animal model of globoid cell leukodystrophy, which is a genetic disease that affects the lysosomal enzyme galactocerebroside beta-galactosidase. This enzyme deficiency causes one of its substrates, galactosylsphingosine (psychosine), to accumulate in myelin-forming cells, which eventually results in their death. In the central nervous system, the death of oligodendrocytes is thought to cause a series of secondary pathological changes. In this study, several techniques were utilized to examine the neuropathology of two different brain regions in the twitcher mouse--the hindbrain and the cerebrum. Neuropathological changes were as follows: (1) demyelination was detected in the hindbrain but not in the cerebrum, (2) a high density of periodic acid-Schiff-positive cells were detected in the hindbrain and to a lesser extent in the cerebrum, (3) astrocyte gliosis was pronounced in both the hindbrain and cerebrum, and (4) macrophages were abundant in both the hindbrain and the cerebrum. We found that Periodic acid-Schiff-positive cells, astrocyte gliosis and macrophage infiltration were present in white and gray matter regions of the cerebrum, while they were generally absent from the granule and molecular layers of the cerebellum. In addition to these studies, we utilized the technique of Fourier transform infrared (FT-IR) microspectroscopy to identify the in situ distribution of psychosine in the brains of twitcher mice. Evidence was obtained that indicates a large accumulation of psychosine in the hindbrain, and to a lesser extent in the white matter of the cerebrum in the twitcher mouse, but not the normal mouse. There was no evidence for the accumulation of psychosine in the molecular layer of the cerebellum from the twitcher or normal mouse. Our conclusions are as follows: (1) pathology is more advanced in the hindbrain compared to the cerebrum, which is likely due to the hindbrain becoming myelinated prior to the cerebrum, (2) demyelination is not necessary for the development of secondary pathological changes, (3) pathology is not limited to white matter in the cerebrum, (4) pathology is not present in all brain regions, i.e. the granule and molecular layers of the cerebellum are devoid of pathological changes, and (5) psychosine accumulates in both the cerebrum and hindbrain, but not in the molecular layer of the cerebellum in the twitcher mouse. This study demonstrates that FT-IR microspectroscopy can be used to correlate chemical changes to histopathological changes in brains from twitcher mice, which suggests that FT-IR microspectroscopy may be a useful tool for studies examining other brain diseases.

Animals↗
PubMed1994

In situ chemical analyses from frozen tissue sections by Fourier transform infrared microspectroscopy. Examination of white matter exposed to extravasated blood in the rat brain.

Fourier transform infrared (FT-IR) microspectroscopy is a powerful technique for obtaining chemical information from tissue sections. Infrared spectra can be collected from individual spots or from several spots along a grid pattern. In the latter example, absorbing bands are interpolated between spectra to generate maps that represent the relative concentrations of chemical groups. In this study, blood was injected into the subcortical white matter of the rat, and the spatial distribution of chemical changes was identified at 2 and 6 days after injection. The absorbances for CH2, H-C = C, C = O, P = O, and HO-C-H were lower at the lesion site compared with the neighboring tissue, which suggests a mechanism of lipid peroxidation. The absorbances for N-H stretch and amide II were greater at the lesion site compared with the surrounding tissue, and the amide II peak was shifted toward lower wave numbers in the affected area. These changes are probably due to the infiltration of blood products, the aggregation of myelin proteins, and/or gliosis in the lesioned tissue. The rate of absorbance change per distance displayed a trend to be more abrupt at 2 days compared with 6 days after injection. We suggest that FT-IR microspectroscopy can be applied to a variety of disease states.

Animals↗
PubMed1987

High-performance liquid chromatographic determination of ferulic acid in wheat milling fractions as a measure of bran contamination.

A high-performance liquid chromatographic method was developed for selective determination of ferulic acid in 7 min in the extracts from wheat flour and ground whole wheat at typical levels of 50 and 500 micrograms/g, respectively. Recovery of 99.9% was obtained when ferulic acid was extracted into dilute sulfuric acid, followed by enzymatic treatment of the extract with an alpha-amylase preparation. The chromatographic system included a 100-mm column packed with Hypersil 5 micron reversed-phase ODS operating isocratically with 12% methanol-citrate buffer (pH 5.4) mixture. The selectivity and sensitivity of both ultraviolet diode array and fluorescence detectors was investigated. The optimum wavelengths selected were 320 nm and 312 nm/418 nm respectively. Relative standard deviations of the analytical procedure were 2.43% and 5.10% for whole wheat and flour samples, respectively.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Preparation of soybean seed samples for FT-IR microspectroscopy.

Typical preparation of seed samples for infrared (IR) microspectroscopy involves imbibition of the seed for varying time periods followed by cryosectioning. Imbibition, however, may initiate germination even at 4 degrees C with associated changes in the chemistry of the sample. We have found that it is possible to section seeds that are sufficiently hard, such as soybeans, on a standard laboratory microtome without imbibition. The use of dry sectioning of unimbibed seeds is reported here, as well as a comparison of different mounting media and modes of analysis. Glycerol, Tissue-Tek, and ethanol were used as mounting media, and the quality of the resulting spectra was assessed. Ethanol was the preferred mountant, because it dried quickly with no residue and thus did not interfere with the spectrum of interest. Analysis in transmission mode using barium fluoride windows to hold the samples was compared with transmission-reflection analysis with sections mounted on special infrared-reflecting slides. The two modes of analysis performed well in different regions of the spectrum. The mode of analysis (transmission vs. transmission-reflection) should be based on the components of greatest interest in the sample.

Desiccation↗
PubMedDate not supplied

Stored wheat insect infestation related to uric acid as determined by liquid chromatography.

Liquid chromatography is used to measure the uric acid content of wheat internally infested by various growth stages of granary weevil (Sitophilus granarius), rice weevil (Sitophilus oryzae), and lesser grain borer (Ryzopertha dominica). Good correlation exists between numbers of insects and uric acid content of grain infested by a given stage of an internally infesting stored product insect, with correlation coefficients ranging from 0.970 to 0.998. Uric acid content of infested grain increases as the insect life cycle progresses, with granary weevil producing the greatest quantities of uric acid followed in order by rice weevil and lesser grain borer. A detection limit for the analytical procedure of less than 1.0 ppm uric acid allows detection of infestation levels as low as one kernel per 100 g grain for late instar granary weevil larvae. This limit is sufficiently sensitive to detect levels of infestation that may be commonly encountered in commerce.

Animals↗